1. Field of the Invention
This invention relates to polyester polymers having improved dyeability and flame retardance and the process for making the same.
2. Description of the Prior Art
It is known to use germanium dioxide as a catalyst in a polycondensation reaction to produce polyesters. Usually, the germanium dioxide is added to the reaction mixture with a glycol, such as ethylene glycol. Unfortunately, crystalline germanium dioxide has a low solubility in the glycols suitable for use in making fiber-forming polymers, resulting in undissolved catalyst which remains in the polymer to give the polymer poor characteristics. Also, low catalyst concentrations require longer reaction times.
One of the properties of polyester fibers in need of improvement is the rate of disperse dye uptake. Generally, the use of carriers and/or high temperatures is required to adequately dye polyesters in a reasonable length of time. Attempts have been made by polyester manufacturers to make polyester easier to dye. One approach has been the use of selected copolymers. Copolymers will generally have a more open structure than homopolymers and it is thus easier for the dye molecule to penetrate a fiber made from the polymer. The composition of the copolymer required may, however, be such as to render other fiber and polymer properties unacceptable or undesirable from a commercial standpoint.
It is known to use certain phosphine oxides as fire retarding agents in polyester polymers. It is also known to use certain dyeability improvers in polyesters for making these polyesters easier to dye. However, it has not been known that, by using certain phosphine oxides with certain dyeability improvers, substantially equivalent dyeability can be achieved with substantially less of the dyeability improver.
In the process of the present invention, a glycol phthalate prepolymer is polycondensed with certain dyeability improvers and certain phosphine oxides, preferably in the presence of a catalyst which is the reaction product of germanium dioxide and a tetraalkyl ammonium hydroxide. The polymer produced has flame-retardant characteristics and is more easily dyed.